Add doc for driver.cancel-tasks-with-stuck-operators-threshold-ms

Author: steveburnett

presto-docs/src/main/sphinx/presto_cpp/properties.rst

@@ -32,6 +32,16 @@ Presto C++ workers.
 These Presto coordinator configuration properties are described here, in 
 alphabetical order. 
 
+``driver.cancel-tasks-with-stuck-operators-threshold-ms``
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+* **Type:** ``string``
+* **Default value:** ``240000`` (40 minutes)
+
+  Cancels any task when at least one operator has been stuck for at 
+  least the time specified by this threshold.
+  
+  Set this property to ``0`` to disable canceling.
+
 ``experimental.table-writer-merge-operator-enabled``
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^